max_input_vars: Adding configurable products with many options will fail at the default of 1000 as magento doesn’t serialise large data sets

memory_limit: Again the admin interface will need more

post_max_size: Either scale down images first, or increase this to allow large uploads. Try to make memory_limit more than the post_max_size as while image uploads do not go directly into RAM, the image processing will generally need as much space as the uncompressed image you’ve just uploaded.

upload_max_filesize: aim for 50% bigger than the photos you will be uploading.

Other issues

Adding configurable products with images often fails –
magento 2 processes images seperately for each virtual product it seems, so often fails to save a configurable product with many options and images.

Remember to restart the apache2 server after changing these settings. If you’re using php_fpm then you’ll need to restart that too.